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CZT Wide Field Gamma-Camera for ESTREMO
P.Ubertini, L.Natalucci, E.M. Quadrini and collaborators
IASF/INAF
L.Natalucci,WHIM Conference,
Roma, 17-18 Jan 2006
INTEGRAL: coded mask FOV and source multiplicity
Many different source types – outside GC and bulge !
b [deg]
SPI
IBIS
SNR
AXP
HMXB
ms-pulsar
XMM (30’)
Diffuse emission (26Al,
from Gal plane
INTEGRAL/IBIS map of Cassiopeia region (20-50 keV)
mosaic 0.7-1.6 Ms, 0.4 – 12 mCrab, den Hartog et al. 2005
60Fe)
l [deg]
• The high energy sky is highly variable and ToO’s are
important
3 deg
GC region, 17-60 keV, 12 frames (36 days)
© M. Revnivtsev & E. Churazov, IKI Moscow/MPA Garching
L.Natalucci,WHIM Conference,
Roma, 17-18 Jan 2006
The transient gamma-ray sky
Sources can appear in ~1000s
Or a few days
Rev 169
Rev 171
Sguera et al., 2005 A&A, in press
Or a few weeks
CZT Wide Field Gamma-Camera for ESTREMO
Very large area, high resolution instrument can be achieved by
natural extension of the INTEGRAL/IBIS concept
with much wider FOV to ensure detection of a large
number of transient events, such as ~100/y
BeppoSAX/WFC heritage
• CdZnTe pixellated detectors
(energy band ~3-300 keV), which
can be assembled in very compact,
modular configuration
• Use of coded mask technique
L.Natalucci,WHIM Conference,
Roma, 17-18 Jan 2006
CZT Wide Field Gamma-Camera for ESTREMO
The stopping power of CdTe/CZT keV is dramatically
higher than Si,Ge (45% at 200 keV, for 3mm thick detector
100 keV Absorption Efficiency
Si
Ge
CdTe/CZT units are also:
CdTe
• operating at room temperature
1,00
0,90
0,80
• performing well in space environment (low
activation, fast recovery after solar flares)
Absorbt ion
0,70
0,60
0,50
0,40
• small pixel manufacturing, pixel arrays
0,30
0,20
0,10
0,00
0
1
2
3
4
5
6
7
8
9
10
Thickness (mm)
CdTe/CZT vs other
• mass production is relatively low cost, and
established technology
L.Natalucci,WHIM Conference,
Roma, 17-18 Jan 2006
CZT Wide Field Gamma-Camera for ESTREMO
WFGC detector
• CZT detection plane with improved
characteristics, achievable within ~ 2 years.
• Effort to achieve extended performance,
like <0.5 keV resolution for detection of Xray features during prompt emission of
GRBs and transients.
• Up to 10000 cm2 can be achieved for the
sensitive area if high energy range is limited
to ˜ 300 keV
the ISGRI MDU
the ISGRI “polycell”
• Power consumption is, in average, 0.5-1 mWatt per channel; total
required: ≤ 100 W for the whole unit FEE.
L.Natalucci,WHIM Conference,
Roma, 17-18 Jan 2006
CZT Wide Field Gamma-Camera for ESTREMO
CZT: technology improvements
Need to improve CZT performances compared to present available
commercial products. The goal is to achieve a factor 5-10 better
energy resolution:
Improvement areas:
• Crystal growth and composition
• Surface treatment and contact depositions
• Front end electronics
• Digital processing electronics
L.Natalucci,WHIM Conference,
Roma, 17-18 Jan 2006
CZT Wide Field Gamma-Camera for ESTREMO
R & D program in Italy for CZT development
A program has started with a consortium of institutes/industries
(P.I. M.Quadrini):
• IMEM-CNR for crystal development
• INAF Milan, Bologna, Rome and Palermo:
Detector development incl. AFEE, DFEE
Signal elaboration, Data Processing
Instrument concept and models
• AAA-I-Laben for AFEE studies
• VENEZIA Tecnologie for evaluation of mass production
Funding from ASI expected. Program already
started
L.Natalucci,WHIM Conference,
Roma, 17-18 Jan 2006
CZT Wide Field Gamma-Camera for ESTREMO
2004 concept
• wide FOV (~2 sr) and
moderate angular resolution
(down to ~ 1-2 arcmin) to detect
and localize transient events
• monitoring capability, but also
detailed characterization of
prompt emission, like GRBs,
fast transients, bright source
Schematic of a possible
outbursts
• extension of the mission range
from X-rays to higher energies
configuration for one WFGC unit
L.Natalucci,WHIM Conference,
Roma, 17-18 Jan 2006
CZT Wide Field Gamma-Camera for ESTREMO
Effective area
We had in the first instance, considered two possible solutions, based on
2 mm and 3 mm thick CZT, respectively.
The thickness of the tungsten
mask will depend on the chosen
CZT thickness.
The effective area for 2mm and 3mm detector thickness.
L.Natalucci,WHIM Conference,
Roma, 17-18 Jan 2006
CZT Wide Field Gamma-Camera for ESTREMO
Imaging (an exercise)
a coded mask design for the
WFGC could be based on
MURA pattern, with 2.4 mm
pitch. The mask pitch is about
1.5 times the size of the basic
detector pixel.
The mask is placed 1m from
detector.
• the coding power is 80%
• the Point Source Location Accuracy, PSLA < 1 arcmin for a >
10sigma detection. The PSLA depends on the signal-to-noise: for this
configuration, is expected to be about 1.5 arcmin at the source
detection limit.
L.Natalucci,WHIM Conference,
Roma, 17-18 Jan 2006
CZT Wide Field Gamma-Camera for ESTREMO
Main difference from 2004 design:
Limit the energy range to <300 keV (no 511)
Possible improvement
Option 1
Less area more FoV (4 detectors with smaller area)
Option 2
• Completely new instrument FoV structure: annular mask and detector (similar to the
one of GRI-ESA Cosmic Vision Study):
• Area 5,000-10,000 cm2
• Single annular modular detector concept
• Thin annular mask (0.5-1 mm W)
• Wide field around the X-Ray telescope for shorter slew, fast repointing, transient event
always within the WFC FoV.
• No high energy calorimeter (4-300 keV)
Plus

10-60 s on-target, lighter package, full time history for each det GRB
Minus 
not easy design, need R&D for detector performance electronics
Others 
On board SW and S/C autonomous operability, TL M resources management
L.Natalucci,WHIM Conference,
Roma, 17-18 Jan 2006
CZT Wide Field Gamma-Camera for ESTREMO
1m
36 CZT modules
S/C
support struct
Mask envelope
Option 1.
Option 2. (schematic, top view)
up to 4 different units located
aside on S/C support
detector modules positioned on
“annulus” on a support
platform, mask ~ 75 cm from
detector, sensitive area 7700 cm2
L.Natalucci,WHIM Conference,
Roma, 17-18 Jan 2006
CZT Wide Field Gamma-Camera for ESTREMO
Sky coverage option 2
~130O
Circular FOV shape
Exposed area in FOV
L.Natalucci,WHIM Conference,
Roma, 17-18 Jan 2006
CZT Wide Field Gamma-Camera for ESTREMO
MASS AND POWER BUDGET OPTION 1
W mask
Tube/Hopper, W
CZT detection plane
Calorimeter/Veto BGO
Electronics
Structure
Harness
Contingency
Total:240
2004
Light version
30 kg
70
40
30
20
20
10
20
15kg
20
40
30
10
12
satellite
13
140 x 2 units = 280 Kg
Power Budget
100 W
100 W x 2 units = 200W
MASS BUDGET OF VERSION 2 UNDER ESTIMATION
L.Natalucci,WHIM Conference,
Roma, 17-18 Jan 2006
CZT Wide Field Gamma-Camera for ESTREMO
Summary of scientific performances option 1
Energy range:
Sensitive area
Energy resolution:
Sensitivity:
4-200 keV without response up to 511
2300 cm2 (48 x 48 cm2)
1 % (E>60KeV)
1 mCrab/day, 20 mCrab in 2000s
(HEO E>40 keV, Solar max)
PSLA:
20 arcsec
Nominal ang. Resolution 10 arcmin
Field of View:
90 x 90 deg @zero response (~2 ster)
(> 50% coding for offset angles <35 deg)
L.Natalucci,WHIM Conference,
Roma, 17-18 Jan 2006
CZT Wide Field Gamma-Camera for ESTREMO
New class of fast transients associated to HMXBs
IGR J17544-2619
Chandra (int’Zand et al 2005)
IBIS detects them very At least up to 7 objects detected of
well! (Negueruela et al. 2005) this kind
L.Natalucci,WHIM Conference,
Roma, 17-18 Jan 2006
CZT Wide Field Gamma-Camera for ESTREMO
New class of fast transients associated to HMXBs
RXTE/PCA (Smith et al 2005)
XTE J1739-302 = IGR J17391-3021
IBIS/ISGRI “zooming”
on source outburst
(Sunyaev et al. 2003)
L.Natalucci,WHIM Conference,
Roma, 17-18 Jan 2006
CZT Wide Field Gamma-Camera for ESTREMO
High localization accuracy is essential in many cases,
and most important with improving sensitivity
Sources in molecular cloud NGC6334, as seen
by Chandra
Hard X-ray source
identified as a
background AGN
ISGRI error box
(Bassani et al., astroph/0510338)
L.Natalucci,WHIM Conference,
Roma, 17-18 Jan 2006